The present invention is directed to a microprocessor analyzer.
Microprocessors (.mu.P) differ from ordinary computers in many significant ways. In a microprocessor the program is typically in read only memory (ROM) and not normally editable especially in a field environment. Important signal points such as flag bits or internal register contents are mechanically and electrically inaccessible.
In contrast, in a normal computer every significant point is accessible. Also there are software routines available to manipulate the computer operation during testing and troubleshooting via a console or terminal.
Thus in analyzing or testing the hardware and software of a typical computer a software approach can be used. But microprocessor testing requires a hardware approach: a new kind of instrument easily attachable to a microprocessor, able to monitor address and data busses, trace program execution and hardware operation passively, or control the microprocessor operation in an interactive mode.
In the past logic analyzers have been used to test microprocessor based systems. These are essentially multitrace oscilloscopes capable of displaying typically up to 16 channels of data in timing diagram or bit pattern form for N steps preceding or following a reference trigger point.
None of the prior art devices have flexibility or capability of detecting errors which are deeply buried in, for example, the multiple nested loops, subroutines, etc. of contemporary microprocessor programs; neither are they capable to operate interactively with a microprocessor.